Alteplase (tPA) dosing for acute ischemic stroke is weight-based but strictly capped, and the total dose is always split into a bolus and an infusion. Getting this wrong in either direction — under-dosing or exceeding the 90 mg ceiling — can compromise the treatment or increase bleeding risk. This calculator implements the FDA label and AHA/ASA guideline dosing formula so the bolus and infusion amounts are correct every time, and it makes clear when the 90 mg cap is limiting the dose below the raw weight-based amount.
How the dose is calculated
The total dose is 0.9 mg/kg of body weight, capped at 90 mg regardless of weight — the cap is reached exactly at 100 kg (0.9 x 100 = 90). Ten percent of the total dose is given as a rapid IV bolus over 1 minute, and the remaining 90% is infused over 60 minutes. This bolus-then-infusion pattern, not a single push or a single slow drip, is specified in the FDA Activase prescribing information and the AHA/ASA 2019 Acute Ischemic Stroke Guideline.
Volumes in mL are computed using the standard reconstituted concentration of 1 mg/mL — both the 50 mg and 100 mg Activase vials are reconstituted with an equal volume of sterile water, so the concentration is the same regardless of which vial size is used.
Why the 90 mg cap matters
Above 100 kg, a strictly linear 0.9 mg/kg calculation would keep increasing the dose — but the FDA label and guideline instead fix the maximum total dose at 90 mg for every heavier patient. This calculator flags whenever the cap is active and shows what the uncapped, weight-based amount would have been, so nothing is silently rounded away. The weight-band reference table on the Total Dose tab shows this cap effect across a full range of body weights at a glance.
Scope, limitations, and required monitoring
This calculator computes dosing only. It does not screen stroke eligibility — the treatment time window (typically within 3 to 4.5 hours of symptom onset or last known well), NIHSS severity, and exclusion criteria such as recent surgery, anticoagulant use, or hemorrhage on imaging must all be confirmed separately through your institution's stroke protocol before alteplase is given. After treatment, standard monitoring includes frequent neurological checks, blood pressure control, a 24-hour hold on antiplatelet and anticoagulant medications, and a follow-up scan before those medications are resumed. In a real stroke emergency, activate your institution's code stroke protocol immediately rather than relying on this or any calculator to make the treatment decision.